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A278008 Number of n X 2 0..2 arrays with every element plus 1 mod 3 equal to some element at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero. 1
0, 6, 30, 198, 1230, 7734, 48510, 304422, 1910190, 11986326, 75213150, 471956358, 2961486990, 18583085814, 116607324990, 731701311462, 4591365157230, 28810436277846, 180783102647070, 1134399003458118, 7118259838467150 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 5*a(n-1) + 8*a(n-2).

Conjectures from Colin Barker, Feb 07 2019: (Start)

G.f.: 6*x^2 / (1 - 5*x - 8*x^2).

a(n) = 2^(-3-n) * ((57-5*sqrt(57))*(5+sqrt(57))^n + (5-sqrt(57))^n*(57+5*sqrt(57))) / 19.

(End)

EXAMPLE

Some solutions for n=4:

..0..1. .0..2. .0..1. .0..1. .0..1. .0..1. .0..1. .0..2. .0..2. .0..2

..0..2. .1..2. .0..2. .0..2. .0..2. .2..2. .1..2. .1..1. .1..1. .1..0

..2..1. .2..0. .2..0. .1..2. .1..2. .1..1. .0..1. .0..1. .0..2. .2..1

..2..0. .2..1. .1..1. .0..0. .1..1. .0..2. .0..0. .2..2. .1..1. .0..1

CROSSREFS

Column 2 of A278014.

Sequence in context: A147517 A294221 A005922 * A325950 A275953 A322170

Adjacent sequences:  A278005 A278006 A278007 * A278009 A278010 A278011

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 08 2016

STATUS

approved

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Last modified September 18 04:22 EDT 2021. Contains 347508 sequences. (Running on oeis4.)